Cerebral palsy (CP) is a devastating disease usually originating from hypoxia-ischemia (H-I) before birth. The costs to society are huge, primarily because of loss of potential productivity and the burden on the individual, family and social institutions, starting at birth and lasting an entire lifetime. Comparatively, CP has a higher index of burden of disease than many neurodegenerative diseases affecting the twilight years of life and yet there is not even a single drug in development for CP. The lack of progress in CP has been because of a lack of a clinically relevant animal model of CP, lack of sufficient resources devoted to this problem, and a lack of a systematic approach to tackle the problem, all of which are addressed in this proposal. We will use the rabbit model of CP that develops after acute placental insufficiency at preterm gestation, based on the clinical paradigm of abruption placenta. This perinatal model is the first to reliably lead to CP, and so it allows us to rigorously test whether putative therapies can prevent the motor deficits of CP in animals. Our previous research has identified new novel designer drugs aimed at neuronal nitric oxide synthase (nNOS) that prevent motor deficits in our animal model in pilot studies. The possible mechanisms leading to brain injury involving nNOS are the production of nitric oxide and subsequent toxic reactive nitrogen species during H-I. This proposal focuses on the biochemical mechanisms of action of the new nNOS inhibitors at a cellular level. It has now become possible to study critical changes in the early phase of H-I injury by the latest development of a surrogate marker of MRI. MRI changes in H-I predict which fetuses will develop postnatal motor deficits. The main question asked in this proposal is whether nNOS is responsible for the critical neuronal injury leading to eventual motor deficits. The first Aim will determine if the nNOS pathway is critical to the generation of postnatal motor deficits. This aim will also select the most effective drugs preventing motor deficits. The second Aim will determine if the nNOS pathway is crucial to the susceptibility of neurons during antenatal H-I injury resulting in postnatal motor deficits. Critical biochemical mechanisms will be studied utilizing the identification of fetuses destined to get postnatal hypertonia and sorting neurons from vulnerable brain regions by high speed flow sorter. The third Aim will determine if the nNOS pathway is crucial to gestational- dependent vulnerability of the neurons to antenatal H-I injury resulting in postnatal motor deficits. New innovations proposed are the systemic integration of MRI as a surrogate marker and high speed sorting into the unique animal model to probe the biochemical basis of specific neuronal injury at a critical time point. The clinical importance of this proposal is that the studies will select the most potent and non-toxic designer drug in the class of nNOS inhibitors for preventing motor deficits. The proposed studies will thus provide the framework for the systematic development of much-needed therapies for CP and thus expedite the clinical application of these therapies.